Summary While approaching MacArthur Lock, Sault Ste. Marie, Michigan, the port shoulder of the downbound, fully loaded bulk carrier AGAWA CANYON struck the port side of the upbound tanker EMERALD STAR, which had just departed the adjacent Poe Lock. At the time of the collision, both vessels were in the confines of the approach walls to the locks and had increased their speeds: the AGAWA CANYON to increase manoeuvrability and the EMERALD STAR to avert collision. There was no pollution and both vessels retained their watertight integrity. However, a significant risk was generated because the EMERALD STAR had been gas-freeing two of the vessel's starboard tanks. Ce rapport est galement disponible en franais. Other Factual Information Circumstances Leading to the Occurrence AGAWA CANYON The AGAWA CANYON is a self-unloading bulk carrier with the bridge forward providing an unobstructed view. Fully loaded with 22 000 tonnes of potash, the vessel was at the maximum permissible Seaway draught. Stopping distance (head reach) in the fully loaded condition, at a speed of 6.5 knots, is 1.2 miles and, at 4.0 knots, 0.8 mile. On 10 April 1998, the vessel was en route to Burns Harbour, Indiana, and was approaching MacArthur Lock at Sault Ste. Marie, Michigan. Winds were from the northwest at 10 to 12 knots and visibility was clear. The initial speed of approach to the western edge of the canal zone appeared, to the lockmaster, to be faster than normal; to the master it appeared normal. After slowing the vessel, the estimated speed of approach was reportedly about 3.0 to 3.5 knots. At approximately 1627 eastern daylight time,(2) the vessel was approaching the lock wall to starboard and was positioned some 550 m west of the International Bridge. The master and helmsman were on the bridge and two linesmen were landed ashore to carry heaving lines that were attached to the vessel's mooring cables. The linesmen help manoeuvre the vessel by placing the ship's mooring cables on bollards ashore; the ship's winches are used to heave up, check or slacken the cables as the ship moves forward using engines and thruster. The closest point to the approach wall was estimated at 3.5 m forward and 3.0 m aft. The bow thruster was used intermittently as the vessel moved forward and the speed was progressively increased. Unable to run along at this speed, the linesmen let go of the lines. The speed was progressively increased to over 6 knots as efforts were made to bring in the bow, which had swung out to port as the stern was sucked to the dock wall.(3) The bow thruster was now in constant use, but at this speed it had little effect. The vessel, now having lost the ability to remain close to the dock wall, moved further out to port, setting up a bow cushion at the starboard bow. Efforts to bring the bow back to the wall by increasing the speed to 7 knots were unsuccessful. Reportedly, astern movement was not used because of the master's concern for stern suction and the possibility that the vessel would sheer to port and cut off the channel. The vessel continued to move further to port, away from the dock wall and into the path of the upbound tanker EMERALD STAR. At 1634:12, the EMERALD STAR, which had just departed the adjacent Poe Lock and was moving along the West Center Pier dock wall, was advised by the AGAWA CANYON on VHF channel 14, that the AGAWA CANYON was experiencing manoeuvring difficulties and that the stern was sucking the wall. A request was also made that the EMERALD STAR move to starboard as far as possible to give the AGAWA CANYON more sea room. At 1635:11, the two vessels collided when the port bow of the AGAWA CANYON struck the port side of the EMERALD STAR a glancing blow between Nos. 1 and 2 ballast tanks. The angle of impact was 25 to 30 degrees to the fore-and-aft line of the EMERALD STAR at an estimated speed of 5.5 to 6.0 knots; the closing speed of the two vessels was about 11 to 12 knots. As the port shoulder scraped along the length of the EMERALD STAR, the starboard bow anchor of the AGAWA CANYON was deliberately dropped, with one shackle (approximately 28 m) of chain into the water. The collision occurred in position latitude 4630'09'' N, longitude 08421'28'' W, some 240 m east of the International Bridge. To prevent the stern of the AGAWA CANYON from striking the EMERALD STAR, the AGAWA CANYON engine controls were set briefly to full ahead with port helm. After clearing the stern of the EMERALD STAR, the AGAWA CANYON then struck the north wall at 1636:02 with some force, 137 m from the Poe Lock entrance. The collision between vessels resulted in indentation of shell plating and associated internals in way of the forecastle deck over a length of 6 m, and collision with the lock wall resulted in corresponding heavier damage at and below the waterline. The vessel was then made fast on the West Center Pier wall to await inspection by the appropriate authorities. There was no delay to other traffic. EMERALD STAR The EMERALD STAR is a tanker with the bridge and accommodation aft and a clear view forward. As per the International Convention for the Prevention of Pollution from Ships (MARPOL) and the United States Oil Pollution Act of 1990 (OPA 90) regulations, the EMERALD STAR is fitted with side and bottom ballast tanks and void spaces. Stopping distance (head reach) for the ballast condition is 457 m at a speed of 6.7 knots and 117 m at 3.5 knots. After discharging some 2800 tonnes of gasoline and some 4400 tonnes of diesel No. 2, the vessel departed Sault Ste. Marie, Ontario, bound for Thunder Bay, Ontario. The voyage was uneventful until the departure from Poe Lock. The lock and dam operating supervisor (locally referred to as the lockmaster) gave permission to the EMERALD STAR to exit the lock at 1628. The EMERALD STAR was under the conduct of the master with the helmsman (and intermittently the watchman) on the bridge. The normal time to exit the lock for a 222 m to 304 m long vessel is about 10 minutes. The EMERALD STAR is a smaller vessel, was in ballast, and in about 6 minutes had cleared the lock (at about 1634) at a speed estimated to have been about 6 mph. As the vessel was departing from Poe Lock, gas-freeing and tank-cleaning operations of Nos. 2 and 4 starboard (cargo) tanks were reportedly underway. The master indicated that gas-freeing began only when the vessel was clear of the dock. Other witnesses indicated that gas-freeing had begun before departure from the lock. In either instance, gas-freeing was taking place close to the lock. Reportedly, the lockmaster indicated that he had called the underway EMERALD STAR by VHF radio, as that vessel was departing the lock, to alert it to perceived concerns with the movements of the AGAWA CANYON. Due to a technical problem, this communication was not tape-recorded and its receipt was not confirmed. The lockmaster also indicated that as the EMERALD STAR cleared the lock upbound, the AGAWA CANYON was just making her landing, west of the International Bridge. At 1634, St. Marys Falls Lock Operations was informed that the EMERALD STAR was clear of the Poe Lock. Some 14 seconds later, the master of the EMERALD STAR, upon receiving a VHF call from the AGAWA CANYON, learned for the first time that the AGAWA CANYON was experiencing manoeuvring difficulty. He had noted earlier that the AGAWA CANYON had initially made what he interpreted to be an unusual landing at the approach wall, but he was concentrating on manoeuvring his own vessel. No clarification was sought, nor was the AGAWA CANYON contacted to confirm if all was well. Instead, it was decided that collision avoidance would be attempted by increasing the speed and manoeuvring through the diminishing space between the bow of the AGAWA CANYON and the wall of the West Center Pier. The bow thruster was not used. The EMERALD STAR first altered course to starboard and then, some 30 seconds later, altered course rapidly to port to reduce the angle of impact. No warning signal on the whistle was sounded to warn the ship's complement and the lock personnel of the impending danger, nor was the general alarm sounded in the internal spaces of the vessel. At 1635:11 the vessels collided. The speed of the EMERALD STAR was estimated to have been about 6.0 to 6.5 knots. The impact of the collision set the EMERALD STAR some 10 m bodily to starboard. The vessel, however, managed to move rapidly ahead and in so doing did not become pinched between the bow of the AGAWA CANYON and the West Center Pier. Damage to the EMERALD STAR comprised indentation to the side shell plating and lifting of the main deck plating in way of a fairlead. The side ballast tanks and void spaces acted as a buffer zone and prevented more serious consequences. There was no pollution. Effectiveness of Bow Thruster Each vessel was fitted with a bow thruster, the performance of which varies with the vessel's speed. While its effectiveness is 100 per cent when the vessel has no headway, it diminishes to 50 per cent at 3 knots, and is nil at 5 knots. Canal Wall Fender Once the AGAWA CANYON port shoulder cleared the EMERALD STARstern, the AGAWA CANYON collided with the opposite wall with such frictional force that the heavy wooden fenders were briefly set on fire until the wash from the vessel coming alongside extinguished the flames. The damage was substantial. The recently installed fendering was intermittently crushed and ripped for a length of approximately 40 m, with intermittent minor damage to the concrete. Certification The master of the AGAWA CANYON held a Canadian Master Inland Waters certificate since 1981. He had sailed intermittently as master and third, second and first mate spanning a period of approximately 30 years. He had been master of this vessel for one year. He was well rested and a recent company medical examination indicated that he was medically fit. The master of the EMERALD STAR has held a Canadian Master Home Trade certificate since 1968. Since 1968 he has served as master on various vessels. He has been sailing on tankers for approximately 20 years. He had been master of this vessel since 13 February 1998 and had been employed as master with the same company since 31 January 1997. He was well rested and a company medical examination had determined him fit for duty. St. Marys Falls Lock Operations and Waterway The southwest pier canal services the entry/exit for both the Poe Lock and the MacArthur Lock. It is 92.65 m wide and has a limiting depth of 8.53 m. The locks are administered and operated by the United States Army Corps of Engineers (USACOE). They are not part of the Canada-United States Seaway system and, thus, St. Lawrence Seaway Regulations do not apply. Neither vessel was required to have a pilot aboard. Poe Lock and MacArthur Lock were at high pool (slack water) and there was no current at the time of the occurrence. The regulatory speed limit is 2.5 mph entering the locks and 6.0 mph departing the locks. Vessels were not prohibited from tank cleaning or gas-freeing while traversing the lock system, nor were they required to report to the lock operations if such operations were taking place. St. Lawrence Seaway Regulations, in contrast, prohibit such activity, and there is a requirement to report such activity to the authorities. As a result of a near-collision in 1996, an internal USACOE memorandum comprised of instructions had been issued by the lock administration to lockmasters stating that tankers are not to exit a lock upbound when a vessel is downbound in the approaches unless the downbound vessel is made fast alongside. This also applies in the opposite direction. This information was not promulgated to vessels through notices to shipping, nor was it required to be. In this instance, the lockmaster had permitted the tanker to exit Poe Lock while the bulk carrier was still manoeuvring underway and was not secured to the approach wall. It was indicated that since the 1996 memorandum there had been hundreds of occasions where tankers were released from a lock to meet vessel traffic in the canal zone. According to the lockmaster, given this fact, the release of the EMERALD STAR on this occasion was not unusual. There is no real-time speed information on vessels moving along the approach wall available to the St. Marys Falls Lock Operations personnel.